Transmission device and transmission method

ABSTRACT

Disclosed are a transmission device and a transmission method with which it is possible to prevent delays in data transmission and to minimize the increase in the number of bits necessary for the notification of a CC to be used, in cases where a CC to be used is added during communication employing carrier aggregation. When a component carrier is to be added to a component carrier set, a setting section provided in a base station: modifies a CIF table that defines the correspondence between code points, which are used as labels for the respective component carriers contained in the component carrier set, and the identification information of the respective component carriers; and assigns a vacant code point to the component carrier to be added, while keeping the correspondence between the code points and the component carrier identification information defined in the CIF table before modification.

TECHNICAL FIELD

The present invention relates to a transmission apparatus and atransmission method.

BACKGROUND ART

3GPP-LTE (3rd Generation Partnership Project Radio Access Network LongTerm Evolution, hereinafter referred to as “LTE”) adopts OFDMA(Orthogonal Frequency Division Multiple Access) as a downlinkcommunication scheme, and SC-FDMA (Single Carrier Frequency DivisionMultiple Access) as an uplink communication scheme (e.g., see non-patentliteratures 1, 2 and 3).

In LTE, a radio communication base station apparatus (hereinafterabbreviated as “base station”) communicates with radio communicationterminal apparatuses (hereinafter abbreviated as “terminals”) byallocating resource blocks (RBs) in a system band to terminals, per timeunit referred to as a subframe. In addition, the base station transmitsto the terminals the control information (resource allocationinformation) to notify the terminals of the result of resourceallocation of downlink data and uplink data. This control information istransmitted to the terminals using downlink control channels such asPDCCHs (Physical Downlink Control Channels). Here, according to, forexample, an allocation number of terminals, the base station controlsthe amount of resources used in transmission of the PDCCHs, that is, thenumber of OFDM symbols on a subframe unit basis. To be more specific,the base station transmits to the terminals using a PCFICH (PhysicalControl Format Indicator Channel), the CFI (Control Format Indicator),which is the information indicating the number of OFDM symbols capableof being used in transmission of the PDCCHs in the first OFDM symbols ofthe subframes. Each of terminals receives the PDCCH in accordance withthe CFI detected from the received PCFICH. Here, each PDCCH occupies aresource formed of one or a plurality of consecutive CCEs (ControlChannel Elements). In LTE, according to the number of information bitsof the control information or the channel state of the terminal, one of1, 2, 4, and 8 is selected as the number of CCEs occupied by the PDCCH(the number of linked CCEs: CCE aggregation level). Here, LTE supportsthe frequency band with the maximum width of 20 MHz as a systembandwidth.

In addition, the base station simultaneously transmits a plurality ofPDCCHs to allocate a plurality of terminals to one subframe. At thistime, in order to identify the destination terminal of each of thePDCCHs, the base station includes a CRC bit masked (or scrambled) withthe ID of the destination terminal in the PDCCH for transmission. Then,the terminal detects the PDCCH addressed to the terminal by performingblind decoding on a plurality of PDCCHs which may be addressed to theterminal, by demasking (or descrambling) CRC bits using its own terminalID.

Furthermore, studies have been underway for a technique to limit the CCEto be the target of blind decoding every terminal, for the purpose ofreducing the number of blind decoding attempts at the terminal. Thistechnique limits the CCE area (hereinafter, referred to as “searchspace”) to be the target of the blind decoding every terminal. In LTE,the search space is randomly formed every terminal, and the number ofCCEs forming the search space is defined every CCE aggregation level ofthe PDCCH. For example, for CCE aggregation levels 1, 2, 4, and 8, thenumbers of CCEs forming the search spaces—that is, the numbers of CCEsto be the targets of the blind decoding—are limited to six candidates (6(=1×6) CCEs), six candidates (12 (=2×6) CCEs), two candidates (8 (=4×2)CCEs), and two candidates (16 (=8×2) CCEs), respectively. Thus, eachterminal needs to perform blind decoding only on the CCEs in the searchspace allocated to the terminal, thus making it possible to reduce thenumber of blind decoding attempts. Here, the search space of eachterminal is configured using the terminal ID of each terminal and a hashfunction for randomization.

Also, LTE adopts ARQ (Automatic Repeat reQuest) for downlink data fromthe base station to the terminals. That is, each of the terminals sendsa response signal indicating the error detection result of downlink datato the base station as a feedback. The terminal performs a CRC on thedownlink data, and then, transmits a response signal (that is, ACK/NACKsignal) indicating an ACK (Acknowledgement) in case of CRC=OK (no error)or a NACK (Negative Acknowledgement) in case of CRC=NG (error exists) asa feed back to the base station. When the response signal transmitted asa feedback indicates the NACK, the base station transmits retransmissiondata to the terminal. Moreover, in LTE, the control technique forretransmitting data, referred to as HARQ (Hybrid ARQ), which combineserror correction coding and ARQ, has been examined. In HARQ, whenreceiving retransmitted data, the terminal can improve reception qualityat the terminal side by combining the retransmitted data and thepreviously-received data including an error.

Moreover, standardization of 3GPP LTE-Advanced (hereinafter referred toas “LTE-A”) to realize faster communication than the LTE has beenstarted. In LTE-A, in order to realize the downlink transmission speedequal to or higher than the maximum 1 Gbps and the uplink transmissionspeed equal to or higher than the maximum 500 Mbps, it is expected tointroduce base stations and terminals (hereinafter referred to as “LTE-Aterminals”) capable of communicating with each other at the widebandfrequency equal to or higher than 40 MHz. In addition, an LTE-Advancedsystem is required to accommodate not only LTE-A terminals but also theterminals supporting an LTE system (hereinafter referred to as “LTEterminals”).

In LTE-A, the carrier aggregation scheme whereby communication isperformed by aggregating a plurality of frequency bands has beenproposed to realize wideband communication of 40 MHz or above (e.g., seenon-patent literature 1). For example, the frequency band having a widthof 20 MHz is defined as the base unit (hereinafter referred to as“component carrier (CC)”) of communication bands. Thus, LTE-A realizesthe system bandwidth of 40 MHz by aggregating two component carriers.Also, a single component carrier accommodates both an LTE terminal andan LTE-A terminal. Additionally, in the following explanation, thecomponent carrier in an uplink is referred to as “uplink componentcarrier”, and the component carrier in a downlink is referred to as“downlink component carrier.”

While it has been studied to support the carrier aggregation by at leastfive component carriers in the LTE-A system, the number of actually usedcomponent carriers differs every terminal according to, for example, arequired transmission rate and the reception capability of each terminalwith the number of component carriers. Here, which component carrier tobe used is configured every terminal. The configured component carrieris referred to as “UE CC set.” The UE CC set is semi-staticallycontrolled by the required transmission rate of the terminal.

In LTE-A, as a method to notify terminals of the resource allocationinformation of each component carrier from a base station, it has beendiscussed to allocate data of different component carriers by a PDCCHtransmitted using a certain component carrier (e.g., see non-patentliterature 4). In particular, studies have been underway to indicate thecomponent carrier which is the allocation target of the PDCCH by using acarrier indicator (CI) in the PDCCH. That is, the CI labels eachcomponent carrier. The CI is transmitted in a field inside of the PDCCH,referred to as “carrier indicator field (CIF).”

Also, it has been considered to report the CIF value of the componentcarrier which is the allocation target, in addition to the CI in the CIF(e.g., see non-patent literature 5).

Also, the above non-patent literature 4 discloses the correspondencebetween a CI value (that is, a code point) and the CC number indicatedby the CI value. That is, when the same CC as the CC which hastransmitted a PDCCH is allocated, CI=1 (when CI starts from 1) isallocated. CI values are associated in ascending frequency order withother CCs. For example, as illustrated in FIG. 1B, when there are threeCCs (CC1, CC2, and CC3 in ascending frequency order) and all three CCsare configured to a terminal (that is, when a UE CC set includes CC1,CC2, and CC3), in the PDCCH transmitted in CC2, CI=1 indicates dataallocation of CC2, CI=2 indicates the data allocation of CC1, and CI=3indicates the data allocation of CC3. Meanwhile, as illustrated in FIG.1A, two out of three CCs are configured to the terminal (for example,when a UE CC set includes CC2 and CC3), CI=1 indicates the dataallocation of CC2 and CI=2 indicates the data allocation of CC3. In thiscase, every time the CC configuration of each terminal (that is, the UECC set) is changed, the correspondence between the CIs and the CCnumbers varies, the CIs being other than the CI allocating the same CC.In the above example, when CC1 is added to the UE CC set in the terminalfor which CC2 and CC3 are configured, the code point of the CIallocating CC3 varies before and after adding the CC.

Here, use of RRC signaling described in non-patent literature 6 tochange the UE CC set (that is, addition and deletion of a CC), forexample, has been considered. To be more specific, an RRC connectionreconfiguration procedure is used to change the UE CC set. In case ofchanging a UE CC set, a base station firstly transmits an RRC connectionreconfiguration message to a terminal to notify the terminal of thechange. The terminal receiving this message changes its configuration,and then, after the change is completed, and sends an RRC connectionreconfiguration complete message to the base station. By receiving theRRC connection reconfiguration complete message, the base station learnsthat the configuration change has been correctly made in the terminal.Here, it normally takes several 10 to 100 ms to communicate thesemessages with each other.

CITATION LIST Non-Patent Literature

NPL 1

-   -   3GPP TS 36.211 V8.3.0, “Physical Channels and Modulation        (Release 8),” May 2008

NPL 2

-   -   3GPP TS 36.212 V8.3.0, “Multiplexing and channel coding (Release        8),” May 2008

NPL 3

-   -   3GPP TS 36.213 V8.3.0, “Physical layer procedures (Release 8),”        May 2008

NPL 4

-   -   3GPP TSG RAN WG1 meeting, R1-100041, “Mapping of CIF to        component carrier” January 2010

NPL 5

-   -   3GPP TSG RAN WG1 meeting, R1-100360, “PCFICH in cross carrier        operation” January 2010

NPL 6

-   -   3GPP TS 36.331 V8.7.0 “Radio Resource Control (RRC)”, September        2009

SUMMARY OF INVENTION Technical Problem

However, according to the correspondence between the CIs and the CCnumbers in the above non-patent literature 4, the addition of a CCvaries the correspondence between the CI code points and the CCs. Forthis reason, during the above RRC connection reconfiguration procedure(that is, a period from transmission of an RRC connectionreconfiguration message from the base station to reception of an RRCconnection reconfiguration complete message), the base station cannotallocate a CC other than the CC used to transmit the PDCCH (CC2 in theabove example). To put it differently, even though the CC is added forthe purpose of increasing the amount of data to be transmitted, forexample, it is impossible to allocate data not only to the CC to benewly added (in the above example, CC2) but also to the CC in use (CC3),until the above reconfiguration is completed. As a result, a delay indata transmission occurs.

On the other hand, when the correspondence between the CIs and the CCnumbers are fixed, the above mentioned problem of the delay in the datatransmission does not occur. For example, when CI=1, CI=2, and CI=3 arefixedly associated with CC1, CC2 and CC3, respectively, no change occursin the correspondence. However, in this case, the number of code points(for example, 3 bits in the system of eight CCs) corresponding to thetotal number of CCs in the system is required for notification of theCCs, regardless of the number of CCs configured to the terminal. As aresult, the number of CIF bits increases. For example, it is alwaysrequired to use 3 bits for notification, even for allocation of four CCs(representable by 2 bits) every terminal. In other words, the number ofCCs supportable by the system is limited by the number of CIF bits inthis case.

It is therefore an object of the present invention to provide atransmission apparatus and a transmission method capable of preventing,when adding a CC to be used in carrier aggregation communication, adelay in data transmission while suppressing an increase in the numberof bits required for notification of the CCs in use.

Solution to Problem

A transmission apparatus according to one aspect of the presentinvention transmits data by a component carrier set including aplurality of component carriers, the transmission apparatus includes: aconfiguration section that corrects, when a component carrier is addedto the component carrier set, a labeling rule associating anidentification information piece of a component carrier with a codepoint used as a label of the component carrier used for transmitting thedata, the configuration section allocating an unused code point to thecomponent carrier to be added, while maintaining a correspondencebetween the identification information piece of the component carrierand the code point according to the labeling rule before correction ismade; a formation section that forms a control signal for datatransmission using each of the plurality of component carriers, thecontrol signal of each of the component carriers being labeled by a codepoint according to the labeling rule corrected by the configurationsection; and a transmission section that transmits a notification signalincluding information about the correction of the labeling rule to areception side of the data.

A transmission method according to an aspect of the present inventiontransmits data by a component carrier set including a plurality ofcomponent carriers, the transmission method includes: a configurationstep of correcting, when a component carrier is added to the componentcarrier set, a labeling rule associating an identification informationpiece of a component carrier with a code point used as a label of thecomponent carrier transmitting the data, the configuration stepallocating an unused code point to the component carrier to be added,while maintaining a correspondence between the identificationinformation piece of the component carrier and the code point accordingto the labeling rule before correction is made; a forming step offorming a control signal for data transmission using each of theplurality of component carriers, the control signal of each of thecomponent carriers being labeled by a code point according to thelabeling rule corrected in the configuration step; and a transmissionstep of transmitting a notification signal including information aboutthe correction of the labeling rule to a reception side of the data.

Advantageous Effects of Invention

According to the present invention, it is possible to provide thetransmission apparatus and the transmission method capable ofpreventing, when adding a CC to be used in carrier aggregationcommunication, a delay in data transmission while suppressing anincrease in the number of bits required for notification of the CCs inuse.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B illustrate a conventional labeling technique;

FIG. 2 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 3 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 4 illustrates operation of the base station and the terminal;

FIGS. 5A, 5B, 5C, 5D, and 5E illustrate operation of the base stationand the terminal;

FIGS. 6A, 6B, and 6C illustrate operation of a base station and aterminal according to Embodiment 2 of the present invention;

FIG. 7 illustrates notification formats;

FIG. 8 illustrates variation 1;

FIG. 9 illustrates CIF table formats according to Embodiment 3 of thepresent invention; and

FIG. 10 illustrates a CIF table format according to Embodiment 3 of thepresent invention.

DESCRIPTION OF EMBODIMENT

Now, embodiments of the present invention will be explained in detailwith reference to the accompanying drawings. Here, in embodiments, thesame components are denoted by the same reference numerals and theiroverlapping explanations are omitted.

Embodiment 1

[Base Station Configuration]

FIG. 2 is a block diagram illustrating a configuration of base station100 according to Embodiment 1 of the present invention. In FIG. 2, basestation 100 includes configuration section 101, memory 102, controlsection 103, PDCCH generating section 104, coding sections 105, 106, and107, modulating sections 108, 109, and 110, allocation section 111,PCFICH generating section 112, multiplexing section 113, IFFT (InverseFast Fourier Transform) section 114, CP (Cyclic Prefix) adding section115, RF transmitting section 116, RF receiving section 117, CP removingsection 118, FFT (Fast Fourier Transform) section 119, extractionsection 120, IDFT (Inverse Discrete Fourier Transform) section 121, anddata receiving section 122.

Configuration section 101 configures one or a plurality of CCs used foruplink and downlink, for each terminal, that is, configures a UE CC set.This UE CC set is configured according to, for example, a requiredtransmission rate of each terminal, the data amount to be transmitted ina transmission buffer, the tolerable amount of delay, and QoS (Qualityof Service). Configuration section 101 also changes the UE CC set onceconfigured.

When initially configuring the UE CC set and every time changing the UECC set, configuration section 101 corrects (updates) a CIF table (thatis, a labeling rule) stored in memory 102. In this CIF table stored inmemory 102, CCs forming the UE CC set are associated with code points ofthe CIFs, respectively.

To be more specific, when adding a new CC to the UE CC set,configuration section 101 adds the new CC, while maintaining the CCsforming the currently configured UE CC set. Also, when correcting theCIF table, configuration section 101 allocates a currently unused CIFcode point to the added CC, while maintaining the relationship betweenthe CIF code points and the CCs forming the currently configured UE CCset. In addition, configuration section 101 also allocates the CC number(hereinafter, this number may be simply referred to as “PDCCH CCnumber”) used to transmit a PDCCH signal including the resourceallocation information related to data transmitted by the added CC. Whendeleting a CC from the CCs forming the UE CC set, configuration section101 deletes only the CC, while maintaining the correspondence betweenthe CIF code points and the undeleted CCs. The details of this CIF tableand the correction process of the CIF table will be described later.

When changing the UE CC set, configuration section 101 notifies laterdescribed terminal 200 of the following information via a process systemgoing through coding section 106. That is, when adding a CC,configuration section 101 notifies terminal 200 of the CC number to beadded, the PDCCH CC number, and the CIF code point allocated to the CCto be added, to terminal 200. Meanwhile, when deleting a CC,configuration section 101 notifies terminal 200 of the CC number to bedeleted. The above configuration is used relatively in a long span. Thatis, the configuration is not changed on a subframe unit basis.

When initially configuring the UE CC set and every time changing the UECC set, configuration section 101 outputs the CC numbers and the PDCCHCC numbers forming the UE CC set, to control section 103 and PDCCHgenerating section 104. Hereinafter, the pieces of information outputfrom configuration section 101 may be collectively referred to as“configuration information.”

Control section 103 generates the resource allocation information (thatis, uplink resource allocation information and downlink resourceallocation information). The uplink resource allocation informationrepresents an uplink resource (for example, PUSCH) to which uplink dataof allocation-target terminal 200 is allocated. Meanwhile, the downlinkresource allocation information represents a downlink resource (forexample, PDSCH) to which downlink data addressed to allocation-targetterminal 200 is allocated. Here, the resource allocation informationincludes: the allocation information of a resource block (RB); the MCSinformation of data; the information relating to HARQ retransmissionsuch as the information (NDI: New Data Indicator) or the RV (RedundancyVersion) information which indicates whether the data is new orretransmission data; the information (CI: Carrier Indicator) of the CCsubject to the resource allocation; and the CFI information of theallocation-target CC.

Control section 103 outputs the resource allocation information to PDCCHgenerating section 104 and multiplexing section 113.

Here, based on the configuration information received from configurationsection 101, control section 103 allocates the resource allocationinformation for allocation-target terminal 200, to the PDCCH arranged inthe downlink component carrier configured in corresponding terminal 200.This allocation process is allocated on a subframe unit basis. Inparticular, control section 103 allocates the resource allocationinformation for allocation-target terminal 200, to the PDCCH arranged inthe downlink component carrier indicated by the PDCCH CC numberconfigured in the terminal 200. Control section 103 allocates a CIF codepoint to each CC subject to the resource allocation, according to theCIF table updated by configuration section 101. A PDCCH is formed by oneor a plurality of CCEs. Furthermore, the number of CCEs used by basestation 100 is configured based on the propagation path quality (CQI:Channel Quality Indicator) and the control information size ofallocation-target terminal 200. By this means, terminal 200 can receivecontrol information at a necessary and sufficient error rate.

Control section 103 determines the number of OFDM symbols used totransmit the PDCCH every downlink component carrier, based on the numberof CCEs used to transmit the PDCCH. Control section 103 generates theCFI information indicating the determined number of the OFDM symbols.Then, control section 103 outputs the CFI information for each downlinkcomponent carrier, to PCFICH generating section 112 and multiplexingsection 113.

PDCCH generating section 104 generates the PDCCH signal to betransmitted in the downlink component carrier indicated by theconfiguration information (in particular, the PDCCH CC number) receivedfrom configuration section 101. This PDCCH signal includes the uplinkresource allocation information and the downlink resource allocationinformation output from control section 103. Furthermore, PDCCHgenerating section 104 adds a CRC bit to the PDCCH signal and then masks(or scrambles) the CRC bit with a terminal ID. Then, PDCCH generatingsection 104 outputs the masked PDCCH signal to coding section 105.

The process described above is performed for each processing targetterminal 200.

Coding section 105 performs a channel coding process on the PDCCH signalof each component carrier input from PDCCH generating section 104 andoutputs the PDCCH signal that has been subjected to the channel codingprocess to modulation section 108.

Modulation section 108 modulates the PDCCH signal input from codingsection 105 and outputs the modulated PDCCH signal to allocation section111.

Allocation section 111 allocates the PDCCH signals of terminals inputfrom modulation section 108, to CCEs inside of the search space of eachterminal in each downlink component carrier. Allocation section 111outputs the PDCCH signal allocated to the CCE to multiplexing section113.

PCFICH generating section 112 generates a PCFICH signal to betransmitted every downlink component carrier, based on the CFIinformation every downlink component carrier input from control section103. PCFICH generating section 112 then outputs the generated PCFICHsignal to multiplexing section 113.

Coding section 106 encodes the configuration information input fromconfiguration section 101 and outputs the encoded configurationinformation to modulating section 109.

Modulation section 109 modulates the encoded configuration informationand outputs the modulated configuration information to multiplexingsection 113.

Coding section 107 performs a channel coding process on the inputtransmission data (downlink data) and outputs the transmission datasignal that has been subjected to the channel coding process tomodulating section 110.

Modulation section 110 modulates the transmission data (downlink data)that has been subjected to the channel coding process and outputs themodulated transmission data signal to multiplexing section 113.

Multiplexing section 113 multiplexes the PDCCH signal input fromallocation section 111, the PCFICH signal input from PCFICH generatingsection 112, the configuration information input from modulation section109, and the data signal (that is, the PDSCH signal) input frommodulation section 110. Here, based on the CFI information of eachdownlink component carrier input from control section 103, multiplexingsection 113 determines the number of OFDM symbols to arrange the PDCCHsevery downlink component carrier. Furthermore, multiplexing section 113maps the PDCCH signal and the data signal (PDSCH signal) to eachdownlink component carrier, based on the downlink resource allocationinformation input from control section 103. Multiplexing section 113 mayalso map the configuration information to the PDSCH. Multiplexingsection 113 then outputs a multiplexed signal to IFFT section 114.

IFFT section 114 converts the multiplexed signal input from multiplexingsection 113 into a time domain waveform. CP adding section 115 thenobtains an OFDM signal by adding a CP to this time domain waveform.

RF transmitting section 116 applies a radio transmission process (suchas up-conversion and D/A conversion) on the OFDM signal input from CPadding section 115 and transmits the result via an antenna.

Meanwhile, RF receiving section 117 performs a radio reception process(such as down-conversion and A/D conversion) on the reception radiosignal received in a reception band via the antenna and outputs theresulting received signal to CP removing section 118.

CP removing section 118 removes a CP from the received signal, and FFTsection 119 converts the received signal from which the CP is removedinto a frequency domain signal.

Extraction section 120 extracts the uplink data of each terminal and thePUCCH signal (e.g., ACK/NACK signal) from the frequency domain signalinput from FFT section 119, based on the uplink resource allocationinformation (e.g., the uplink resource allocation information in foursubframes ahead) input from control section 103. IDFT section 121converts the signal extracted by extraction section 120 into a timedomain signal and outputs the time domain signal to data receivingsection 122.

Data receiving section 122 decodes uplink data out of the time domainsignal input from IDFT section 121. Then, data receiving section 122outputs the decoded uplink data as received data.

[Terminal Configuration]

FIG. 3 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1 of the present invention. Terminal 200communicates with base station 100 by using a plurality of downlinkcomponent carriers. When the received data includes an error, terminal200 stores the received data in an HARQ buffer, and at the time ofretransmission, combines retransmission data with the received datastored in the HARQ buffer and decodes the resulting combined data.

In FIG. 3, terminal 200 includes RF receiving section 201, CP removingsection 202, FFT section 203, demultiplexing section 204, configurationinformation receiving section 205, PCFICH receiving section 206, CIFtable configuring section 207, PDCCH receiving section 208, PDSCHreceiving section 209, modulating sections 210 and 211, DFT (DiscreteFourier Transform) section 212, mapping section 213, IFFT section 214,CP adding section 215, and RF transmitting section 216.

RF receiving section 201 is capable of changing a reception band, andchanges the reception band, based on the band information input fromconfiguration information receiving section 205. Then, RF receivingsection 201 applies a radio reception process (such as, down-conversionand A/D conversion) to the reception radio signal (here, OFDM signal)received in the reception band via an antenna and outputs the resultingreceived signal to CP removing section 202.

CP removing section 202 removes a CP from the reception signal. FFTsection 203 converts the received signal from which the CP is removedinto a frequency domain signal and outputs this frequency domain signalto demultiplexing section 204.

Demultiplexing section 204 demultiplexes the signal input from FFTsection 203 into a higher layer control signal (e.g., RRC signaling)including configuration information, a PCFICH signal, a PDCCH signal,and a data signal (i.e., PDSCH signal.) Then, demultiplexing section 204outputs the control signal to configuration information receivingsection 205, the PCFICH signal to PCFICH receiving section 206, thePDCCH signal to PDCCH receiving section 208, and the PDSCH signal toPDSCH receiving section 209.

Configuration information receiving section 205 reads the followinginformation from the control signal received from demultiplexing section204. That is, this read information means the information configured tothe terminal, the information including: uplink component carrier anddownlink component carrier for use in data transmission; informationindicating a downlink component carrier for use in transmitting a PDCCHsignal to which resource allocation information for each componentcarrier is allocated; and the CIF code point corresponding to an addedor removed CC.

Configuration information receiving section 205 outputs the readinformation to CIF table configuring section 207, PDCCH receivingsection 208, RF receiving section 201, and RF transmitting section 216.Furthermore, configuration information receiving section 205 reads theterminal ID configured to the terminal from the control signal receivedfrom demultiplexing section 204 and outputs the read information toPDCCH receiving section 208.

PCFICH receiving section 206 extracts the CFI information from thePCFICH signal received from demultiplexing section 204. That is, PCFICHreceiving section 206 obtains the CFI information indicating the numberof OFDM symbols used for the PDCCH to which the resource allocationinformation is allocated, for each of a plurality of downlink componentcarriers configured in the terminal. PCFICH receiving section 206outputs the extracted CFI information to PDCCH receiving section 208 andPDSCH receiving section 209.

CIF table configuring section 207 corrects (updates) the CIF table heldby PDCCH receiving section 208, based on an added or removed CC numberreceived from configuration information receiving section 205 and theCIF code point allocated to the CC. This correction process correspondsto the correction process in base station 100.

PDCCH receiving section 208 performs blind decoding on the PDCCH signalreceived from demultiplexing section 204, to obtain the PDCCH signal(resource allocation information) addressed to the terminal. Here, thePDCCH signal is allocated to each CCE (i.e., PDCCH) arranged in thedownlink component carrier configured to the terminal, the CCE indicatedby the information received from configuration information receivingsection 205.

To be more specific, for each downlink component carrier, PDCCHreceiving section 208 specifies the number of OFDM symbols in which thePDCCH is arranged, based on the CFI information received from PCFICHreceiving section 206. PDCCH receiving section 208 then calculates thesearch space of the terminal by using the terminal ID received fromconfiguration information receiving section 205.

PDCCH receiving section 208 then demodulates and decodes the PDCCHsignal allocated to each CCE in the calculated search space.

PDCCH receiving section 208 performs blind decoding on each PDCCH signalperforming resource allocation of data of each component carrier. Forexample, when there are two component carriers (downlink componentcarrier 1 and downlink component carrier 2) and the PDCCH signals ofboth component carriers are transmitted from CC1, PDCCH receivingsection 208 performs the blind decoding on the PDCCH signal performingdata allocation of downlink component carrier 1 and blind decoding onthe PDCCH signal performing data allocation of downlink componentcarrier 2, on CC1.

PDCCH receiving section 208 determines the decoded PDCCH signal as thesignal addressed to the terminal, the decoded PDCCH signal resulting inCRC=OK (no error) after demasking a CRC bit using the terminal ID of theterminal indicated by the terminal ID information.

PDCCH receiving section 208 outputs the downlink resource allocationinformation included in the PDCCH signal addressed to the terminal toPDSCH receiving section 209, and outputs the uplink resource allocationinformation to mapping section 213. Meanwhile, when no PDCCH signalresulting in CRC=OK is detected, PDCCH receiving section 208 determinesthat the current subframe does not include data allocation addressed tothe terminal and stands by until the next subframe.

Here, in the downlink resource allocation information included in thePDCCH signal, the CIF code point indicates the CC used for transmittingdownlink data. Thus, with reference to the CIF table updated by CIFtable configuring section 207, PDCCH receiving section 208 converts theCIF code point included in the downlink resource allocation informationinto a CC number and then outputs the downlink resource allocationinformation to PDSCH receiving section 209. Here, the CIF table isstored in the memory (not shown) included in PDCCH receiving section208.

PDSCH receiving section 209 extracts the received data (downlink data)from the PDSCH signal received from demultiplexing section 204, based onthe downlink resource allocation information and CFI information of aplurality of downlink component carriers received from PDCCH receivingsection 208, and the CFI information of the CC where the PDCCH signal istransmitted, the CFI information received from PCFICH receiving section206. Also, when the CC used to transmit the PDCCH signal is differentfrom the CC used to transmit the PDSCH signal, the CFI information isobtained from the decoded PDCCH signal.

Furthermore, PDSCH receiving section 209 performs error detection on theextracted reception data (downlink data). As a result of the errordetection, PDSCH receiving section 209 generates a NACK signal as anACK/NACK signal when the reception data includes an error, whereas PDSCHreceiving section 209 generates an ACK signal as the ACK/NACK signalwhen the reception data includes no error. Then, PDSCH receiving section209 outputs the ACK/NACK signal to modulation section 210. When thereception data includes an error, PDSCH receiving section 209 stores theextracted reception data in an HARQ buffer (not shown). Upon receipt ofretransmitted data, PDSCH receiving section 209 combines thepreviously-received data stored in the HARQ buffer with theretransmitted data and performs the error detection on the resultingcombined signal. When base station 100 transmits the PDSCH signal usingspatial multiplexing, for example, MIMO (Multiple-Input Multiple-Output)and thereby transmits two data blocks (Transport Blocks), PDSCHreceiving section 209 generates ACK/NACK signals for the respective datablocks.

Modulation section 210 modulates the ACK/NACK signal received from PDSCHreceiving section 209. When base station 100 transmits two data blocksby spatially-multiplexing the PDSCH signal in each downlink componentcarrier, modulation section 210 applies QPSK modulation on the ACK/NACKsignal. Meanwhile, when base station 100 transmits one data block,modulation section 210 applies BPSK modulation on the ACK/NACK signal.That is, modulation section 210 generates one QPSK signal or BPSK signalas the ACK/NACK signal of each downlink component carrier. Modulationsection 210 then outputs the modulated ACK/NACK signal to mappingsection 213.

Modulation section 211 modulates transmission data (uplink data) andoutputs the modulated data signal to DFT section 212.

DFT section 212 converts the data signal input from modulation section211 into a frequency domain signal and outputs the resulting pluralityof frequency components to mapping section 213.

Mapping section 213 maps the data signal input from DFT section 212 tothe PUSCH arranged in the uplink component carrier, according to theuplink resource allocation information input from PDCCH receivingsection 208. Mapping section 213 also maps the ACK/NACK signal inputfrom modulation section 210 onto the PUCCH arranged in the uplinkcomponent carrier.

Here, modulation sections 210 and 211, DFT section 212, and mappingsection 213 may also be provided every uplink component carrier.

IFFT section 214 converts a plurality of frequency components mapped tothe PUSCH into a time-domain waveform, and CP adding section 215 adds aCP to the time-domain waveform.

RF transmitting section 216 is capable of changing a transmission band,and configures the transmission band, based on the band informationreceived from configuration information receiving section 205. Then, RFtransmitting section 216 applies a radio transmission process (such as,up-conversion and D/A conversion) to the signal to which the CP isadded, to transmit the result via an antenna.

[Operations of Base Station 100 and Terminal 200]

Operations of base station 100 and terminal 200 having the abovementioned configurations will be described. Here, in particular, theprocess to correct a CIF table will be explained, the process beingperformed for a change in a UE CC set.

FIG. 4 illustrates how CCs forming a UE CC set vary with time. FIG. 5illustrates the conditions of the CIF table in time intervalsillustrated in FIG. 4. When the CIF consists of two bits, there are fourcode points represented by bit sequences 00, 01, 10, and 11,respectively. Here, a case will be described assuming that CIs=1, 2, 3,and 4 correspond to the bit sequences 00, 01, 10, and 11, respectively.

As illustrated in FIG. 4, when the power of terminal 200 is turned on,terminal 200 starts to communicate with base station 100 in one CC (inFIG. 4, CC2) according to operations such as a cell search and randomaccess as in LTE.

Base station 100 then adds a CC to terminal 200 due to, for example,increase of the amount of data. Here, configuration section 101 corrects(updates) the CIF table stored in memory 102 in base station 100. To bemore specific, when adding a new CC to the UE CC set, configurationsection 101 adds the new CC while maintaining the CCs forming thecurrently configured UE CC set. In the correction of the CIF table,configuration section 101 allocates the currently unused CIF code pointto the added CC, while maintaining the relationship between the CIF codepoints and the CCs forming currently configured UE CC set. Configurationsection 101 also allocates “PDCCH CC number.”

For example, in FIG. 4, CCs are added at the start timings of intervalsB, C, and E, respectively. The conditions of the CIF tables in theintervals B, C, and E are illustrated in FIG. 5B, C, and E,respectively. For example, CC1 is added between FIG. 5B and FIG. 5C. InFIG. 5C, CC1 is associated with CIF code point 3 unused in FIG. 5B,while the relationship between the CCs forming the UE CC set and the CIFcode point in FIG. 5B is maintained.

As illustrated in FIG. 4, in interval C, the information of data (PDSCH)allocation in CC1, 2, and 3 is notified to terminal 200 by the PDCCH ofCC2. That is, “PDCCH CC number” is 2 at this time.

Also, when deleting a CC from the CCs forming the UE CC set,configuration section 101 deletes only the CC, while maintaining thecorrespondence between the CIF code points and the CCs not to bedeleted.

For example, CC1 is deleted between FIG. 5C and FIG. 5D. In FIG. 5D, thecorrespondence between the CIF code points and CCs 2 and 3 other thanCC1 in FIG. 5C is maintained.

The correction process by CIF table configuring section 207 of terminal200 corresponds to the correction process in base station 100.

As described above, even when the CIF table is changed in associationwith the change of the UE CC set (that is, addition or deletion of aCC), the correspondence between the CIF code points and CCs unrelated tothe change is maintained. That is, it is possible to allocate data tothe CCs unrelated to the change by using the previously allocated codepoints as is, even during an RRC connection reconfiguration procedurerequired on changing the UE CC set. By this means, it is possible toprevent a delay in data transmission. Also, the usage of more CCs canimprove the data throughput.

Furthermore, since the CIF code points are allocated only to the CCsactually configured to terminal 200, the number of bits required fornotifying terminal 200 of the CCs from base station 100 can be only thenumber of CCs supported by terminal 200. For example, even in case of asystem supporting eight CCs, the number of bits required for notifyingterminal 200 of the CCs from base station 100 can be only two bits whenthe number of CCs supported by terminal 200 is four. That is, even whenthe number of CCs in the entire system increases, there is no need toincrease the number of CIF bits and hence it is possible to reduce theamount of control information.

According to the present embodiment described above, in base station100, when adding a component carrier to a component carriers set (UE CCset), configuration section 101 corrects the CIF table associating theidentification information of the component carriers with the codepoints used as the labels of the component carriers included in the UECC set, and then allocates an unused code point to the component carrierto be added, while maintaining the correspondence between theidentification information of the component carriers and the code pointsin the state before the CIF table is corrected. Control section 103forms control signals (PDCCHs) related to data transmission using aplurality of component carriers, respectively, and the control signalsof the respective component carriers are labeled by the code pointsaccording to the CIF table corrected by configuration section 101. Thetransmission section including configuration section 101, coding section106, and modulating section 109 transmits a notification signalincluding the information related to the correction of the CIF table toterminal 200.

As a result, it is possible to suppress the number of bits required fornotification of the CCs in use and also to prevent the delay in the datatransmission.

In addition, the CIF table in memory 102 may be maintained every CC usedto transmit a PDCCH. That is, in case of adding a CC, the CIF table ofthe allocated PDCCH CC is corrected. For example, since CC2 is allocatedas a PDCCH CC, the CIF table of CC2 is corrected in the above example.As another example, let us consider a case where CC2 is configured asthe PDCCH CC for both CC2 and CC3 in the UE CC set (that is, the stateof FIG. 4B). Here, in case of adding CC1 and CC4, CC1 may be configuredas the PDCCH CC of CC1 and CC4, and CIF code points 1 and 2 may beallocated to CC1 and CC4. In this case, the CIF table of CC1 iscorrected. In a case where the CIF table is maintained every CC asabove, allocation of the same CIF code point numbers is possible whenthe PDCCH CCs are different. Thus, the number of CIF bits required forCC notification can be reduced.

Embodiment 2

In Embodiment 2, the CIF code point reports a CFI value in addition tothe CC number which is the target of the data allocation. That is, inthe CIF table, the pair of the CC number and the CFI value is associatedwith the CIF code point. Here, the CFI value at the top of the subframeis transmitted to all terminals from each of the CCs by a PCFICH(Physical Control Format Indicator Channel). In a heterogeneous networkenvironment where a macrocell and a femtocell exist, the PCFICH may notbe received with sufficient reliability. In such an environment, it ispossible to increase the reliability in CFI notification, by includingthe CFI value related to a certain CC in a PDCCH signal transmitted fromanother CC.

The basic configurations of a base station and a terminal according toEmbodiment 2 are common to Embodiment 1, and will therefore be describedusing FIGS. 2 and 3.

When adding a CC, configuration section 101 of base station 100according to Embodiment 2 basically allocates pairs each including theCC to be added and a corresponding one of all CFI values to differentCIF code points, respectively. Also in Embodiment 2, configurationsection 101 basically allocates a currently unused CIF code point to theadded CC, while maintaining the relationship between the CIF code pointsand the CCs forming the currently configured UE CC set. When deleting aCC from the CCs forming the UE CC set, configuration section 101 deletesonly the CC, while maintaining the correspondence between the CIF codepoints and the CCs not to be deleted. At this time, the correspondencerelated to the CC to be deleted is all deleted.

Also, CIF table configuring section 207 of terminal 200 corrects(updates) the CIF table held by PDCCH receiving section 208, based onthe added or deleted CC number received from configuration informationreceiving section 205, the CIF code point and the CFI value allocated tothe CC.

Operations of base station 100 and terminal 200 having the abovementioned configurations will be described.

In the present embodiment, base station 100 and terminal 200 share thetable representing the relationship of the CIF code points, the CCnumbers, and the CFI values. In case of adding a CC, up to three CIFcode points corresponding to CFIs=1, 2, and 3 are allocated, and thenthe information related to the allocated CIF code points is notified toterminal 200 from base station 100. When the number of configured CCs islarge, the number of CFI values that can be notified for the added CCsmay be two or one. Thus, when notifying terminal 200 of the informationrelated to the CC in case of adding a CC, base station 100 also notifiesterminal 200 of the number of allocated code points. This notificationformat is illustrated in FIG. 7.

FIG. 6 illustrates how the CIF table varies when CCs are added. Inparticular, FIG. 6 illustrates how the CIF table varies when CC1 and CC4are sequentially added to terminal 200 performing communication usingCC2 and CC3. Here, it is assumed that the CC used to transmit a PDCCH isCC2.

As illustrated in FIG. 6, when adding CC1, configuration section 101allocates the pairs each including the CC to be added and acorresponding one of all CFI values to different CIF code points,respectively. That is, since CFIs=1, 2, and 3 are prepared here,different CIF code points are allocated to the three pairs of CC1 andCFIs=1, 2, and 3, respectively. In the state of FIG. 6A, since CIF codepoints 5 to 8 are unused, three of these CIF code points are allocatedto the three pairs of CC1 and CFIs=1, 2, and 3, respectively. Here, inparticular, the CIF code point with a smaller number is preferentiallyallocated in ascending order.

As illustrated in FIG. 6C, when adding CC4, configuration section 101allocates the pairs each including the CC to be added and acorresponding one of all CFI values to different CIF code points,respectively. Here, the pair of CC4 and CFI=2 is allocated to CIF codepoint 8 which is unused. Meanwhile, instead of the pair of CC3 andCFI=3, the pair of CC4 and CFI=1 is allocated to CIF code point 4 whichhas been previously allocated to the pair of CC3 and CFI=3. That is, thepair of CC3 and CFI=3 is overwritten by the pair of CC4 and CFI=1.

That is, depending on conditions, configuration section 101 may allocatethe pairs each including the CC to be added and a corresponding one ofsome CFI values to different CIF code points, respectively.

Configuration section 101 can select which CIF code point correspondingto a CFI value to overwrite, from a plurality of CIF code pointsallocated to any CC. That is, while the pair of CC3 and CFI=3 isoverwritten in FIG. 6C, the pair of CC3 and CFI=1 or the pair of CC3 andCFI=2 may be overwritten instead.

Configuration section 101 can also select which pair to allocate to theCIF code point, from the pairs each including the CC to be added and acorresponding one of all the CFI values. That is, while two pairs of CC4and CFIs=1 and 2 are selected from three pairs of CC4 and CFIs=1, 2, and3 in FIG. 6C, two pairs of CC4 and CFIs=2 and 3 may be selected or twopairs of CC4 and CFIs=1 and 3 may be selected instead. The pair actuallyallocated to the CIF code point is selected according to, for example,the cell environment. For example, since a cell with a large cell radius(for example, macrocell) accommodates a large number of terminals, manyPDCCH resources are often required. Thus, a large value (for example, 2or 3) is preferable as the CFI value representing a PDCCH resourceregion. In contrast, since the cell with a small cell radius (forexample, picocell and femtocell) accommodates a small number ofterminals, the CFI value representing the PDCCH resource region may besmall. Thus, 1 or 2, for example, is selected as the CFI value in thiscase. In a cell such as a hotspot where the number of terminalsincreases or decreases drastically, 1 or 3 may be selected as the CFIvalue. Then, the information related to the selected pair is separatelynotified.

FIG. 7 illustrates the notification formats of the CIF code points. InFIG. 7, the upper part illustrates a format to report three CIF codepoints, the middle part illustrates a format to report two CIF codepoints, and the lower part illustrates a format to report one CIF codepoint.

As illustrated in FIG. 7, each format provides the same number ofregions to store the CIF code points as the number of CFI valuesrequired to be notified. Furthermore, each storage region is associatedwith a different CFI value. This storage region may be referred to as“notification field.”

As described above, even when the CIF table is changed in associationwith a change in the UE CC set (that is, addition or deletion of a CC),the correspondence between the CIF code points and the CCs unrelated tothe change is maintained. Even when a pair related to a previouslyallocated CC is overwritten, only some of the pairs related to the CC isoverwritten, so that the CIF code points of the pairs not overwrittenare maintained.

That is, it is possible to allocate data to the pairs unrelated to thechange by using the previously allocated code points as is, even duringan RRC connection reconfiguration procedure required on changing the UECC set. By this means, it is possible to prevent the delay in the datatransmission.

By selecting the code point to overwrite according to the necessary CFIvalue, it is possible to select the CFI value likely to be usedaccording to a cell environment, for example. Also, configuring the CFIvalue in association with the CC in case of adding the CC makes itpossible to configure the CFI value according to the cell environment,for example.

When deleting CC4 from the state of FIG. 6C, it is possible toseparately allocate CIF code point 4 to the pair of CC3 and CFI=3, or toautomatically return to the table of FIG. 6B which is the previousstate. By this means, when the number of CCs included in the UE CC setdecreases, it is possible to set three CFI values to be reportable,without separately reporting the CIF code point.

Here, there are some variations of the technique for notifying terminal200 of pairs in case of allocating only pairs of the CC to be added andsome of the CFI values to CIF code points.

(Variation 1)

In variation 1, the CIF table associates the CIF code points with theCFI values, respectively, in advance. That is, in the example of FIG. 8,the CFI values are fixedly allocated to CIF code points 2 to 8,respectively.

Thus, once the CFI value to be used is determined, the candidate usableCIF code points are narrowed down. Thus, the selection process ofconfiguration section 101 can be simplified. Also, when base station 100notifies terminal 200 of a CIF code point, the corresponding CFI valueis specified. For this reason, base station 100 need not separatelynotify terminal 200 of the CFI value.

(Variation 2)

Variation 2 uses a notification format capable of storing a largernumber of CIF code points than the number of actually required CFIvalues. Here, for ease of explanation, a case to use the notificationformat of the upper part in FIG. 7.

Here, when only two out of three CFI values are allocated to additionalCCs, it is notified as follows.

That is, in a case where three notification fields included in thenotification format report CIF code points=2, 2, and 3, respectively,this means that the CFI values corresponding to CIF code points=2 and 3are 1 and 3, respectively. Also, in a case where the three notificationfields report CIF code points=2, 3, and 3, respectively, this means thatthe CFI values corresponding to CIF code points=2 and 3 are 1 and 2,respectively. Also, in a case where the three notification fields reportCIF code points=2, 3, and 2, respectively, this means that the CFIvalues corresponding to CIF code points=2 and 3 are 2 and 3,respectively. To put it more specifically, the mapping patterns of theCIF code points to a plurality of notification fields are associatedwith the combinations of a plurality of CFI values.

By this means, it is possible to report the CFI value to be actuallyused, without additional signaling to report which CFI value is used.

(Variation 3)

Variation 3 uses a notification format capable of storing the samenumber of CIF code points as the maximum number of CFI values. Here, forease of explanation, an explanation will be given of a case where thenotification format shown in the upper part of FIG. 7 is used.

Here, when only two out of three CFI values are allocated to theadditional CCs, it is notified as follows.

For example, when two CIF code points 6 and 8 are to be associated withCFIs=2 and 3, respectively, three notification fields store CIF codepoints =1, 6, and 8,respectively. Here, when the added CC and the CCused to transmit a PDCCH are the same, CIF=1 is used as a ruleregardless of the notification content of the CIF code point. By thismeans, when CIF=1 is stored in a notification format, this CIF codepoint can be treated as invalid. Thus, as described above, when threenotification fields store CIF code points=1, 6, and 8, respectively,only CIF code points 6 and 8 are valid. Thus, CFI values=2 and 3corresponding to the fields storing those code points, respectively, canbe notified.

By this means, it is possible to report a CFI value to be actually used,without additional signaling to report which CFI value is used.

Embodiment 3

Embodiment 3 defines a plurality of CIF tables with different numbers ofcode points usable per CC, and configures in advance which table to useevery terminal. By this means, it is possible to use the CIF tableappropriate for the reception capability (UE capability) of eachterminal, the communication status of each terminal, and the cellenvironment.

The basic configurations of a base station and a terminal according toEmbodiment 3 are common to Embodiment 1, and will therefore be describedusing FIGS. 2 and 3.

Memory 102 of base station 100 according to Embodiment 3 stores a groupof CIF table formats. FIG. 9 illustrates an example of the group of theCIF table formats. As illustrated in FIG. 9, each of the CIF tableformats includes a plurality of subsets. This subset is a unit to beallocated to one CC. Each subset includes one or a plurality of CIF codepoints. Also, the CIF table formats differ each other in at least one ofthe number of CIF code points included in the subsets (in other words,the number of subsets included in each CIF table), and the combinationof the CFI values included in a subset.

For each terminal 200, configuration section 101 selects and configureswhich table format to use from a plurality of CIF table formats storedin memory 102. The information of this configured CIF table format isnotified to terminal 200 as configuration information. This table formatis configured and notified to terminal 200 when terminal 200 transitionsfrom an idle mode to an active mode to start communication or when aradio bearer is established. That is, the configuration or notificationof the table format is set in a longer interval than a change in the UECC set.

When adding a CC to terminal 200, configuration section 101 notifiesterminal 200 of the subset number of the CIF table format that isconfigured in advance every terminal 200 and that is allocated to the CCto be added. By this means, terminal 200 can associate the additional CCwith all CIF code points included in the notified subset number.

CIF table configuring section 207 of terminal 200 according toEmbodiment 3 configures the table format notified from the base stationin PDCCH receiving section 208. Also, CIF table configuring section 207updates the CIF table by the subset number notified in case of CCaddition.

Operations of base station 100 and terminal 200 having the abovementioned configurations will be described referring to FIG. 9.

As illustrated in FIG. 9, each CIF table format includes a plurality ofsubsets. A CIF code point is allocated to the subsets, by defining oneor a plurality of CIF code points as an allocation unit. In table format1, each subset includes three CIF code points. In each of table formats2 to 4, basically, each subset includes two CIF code points.

Also, the CIF table formats differ each other in at least one of thenumber of CIF code points included in the subsets (in other words, thenumber of subsets included in each CIF table), and the combination ofthe CFI values included in a subset. That is, table format 1 differsfrom table formats 2 to 4, in the number of the CIF code points includedin the subsets. Also, table formats 2 to 4 differ each other in thecombination of CFI values included in the subsets. That is, in tableformat 2, the combination of the CFI values included in the subsets is 1and 2, while the combination of the CFI values included in the subsetsis 2 and 3 in table format 3, and the combination of the CFI valuesincluded in the subsets is 1 and 3 in table format 4.

In each table format, the subset including CIF=8 includes only one CIF.For CIF=8, the largest CFI value is selected and configured from CFIvalues allocatable for each table format. That is, as the CFI value, 2,3 and 3 are respectively configured in table formats 2, 3 and 4. Thereason for the above configurations is as follows. That is, even whenthe number of OFDM symbols in the control channel region of a certain CCis lower than the CFI value reportable by a table format configured in acertain terminal 200, as long as the first OFDM symbol to which a datasignal (PDSCH) addressed to the terminal 200 is mapped, corresponds tothe value notified by CFI, it is possible to prevent the control channeland the data signal from overlapping each other. Meanwhile, when a smallCFI value is configured in CIF=8, the number of OFDM symbols in acontrol channel region of a certain CC often exceeds the CFI valueconfigured in CIF=8. As a result, the control channel and the datasignal overlap each other in this case. Thus, one of channels may not beable to be transmitted. In view of the above, for CIF=8, the largest CFIvalue is selected and configured from the CFI values allocatable in eachtable format.

For each terminal 200, configuration section 101 selects and configureswhich table format to use, from a plurality of CIF table formats storedin memory 102, and then notifies each terminal 200 of the configurationinformation.

Configuration section 101 configures table format 1 for the terminalcapable of receiving signals using up to three CCs, and configures tableformats 2 to 4 for the terminal capable of receiving signals using equalto or more than four CCs. Also, configuration section 101 configurestable formats 2 to 4 which can configure a large number of CCs (that is,a large number of included subsets), for the terminal with therequirement of high speed transmission, and configures table 1 for theterminal without the requirement of high speed transmission.

Also, configuration section 101 can configure the table format on a cellunit basis. For example, configuration section 101 assigns andconfigures table formats 2 to 4 for each terminal in a cell operatedwith a large number of CCs causing other CCs to perform data allocationnotification, and assigns and configures table format 1 in a celloperated with a small number of CCs causing other CC to perform dataallocation notification.

In a cell with a large cell radius, configuration section 101 configuresa table format in which a large CFI value is allocated to each subset.That is, the cell with a large cell radius (for example, macrocell)accommodates a large number of terminals. For this reason, many PDCCHresources are often required. Thus, the table format in which a largeCFI value (for example, 2 and 3) is allocated to each subset isconfigured in such a cell.

In contrast, in a cell with a small cell radius, configuration section101 configures a table format in which a small CFI value is allocated toeach subset. That is, the cell with a small cell radius (for example,pico cell or femtocell) accommodates a small number of terminals. Forthis reason, the required amount of PDCCH resource region is small inmany cases. Thus, the table format in which a small CFI value (forexample, 1 and 2) is allocated to each subset is configured in such acell.

In a cell where the number of terminals increases or decreasesdrastically (for example, a hotspot), configuration section 101configures the table format in which both a large CFI value and a smallCFI value (for example, 1 and 3) are allocated to each subset.

As described above, for each terminal 200, configuration section 101selects and configures which table format to use, from a plurality ofCIF table formats stored in memory 102. Also, a plurality of the CIFtable formats stored in memory 102 differ each other in at least one ofthe number of CIF code points included in the subsets (in other words,the number of subsets included in each CIF table), and the combinationof the CFI values included in a subset.

Accordingly, when adding a CC, configuration section 101 only has tonotify each terminal 200 of a subset number. Thus, it is possible toreduce the number of bits used for notification. Defining the tableformat in advance limits the combination of a plurality of CIF codepoints used for allocation to a certain CC. By this means, it ispossible to simplify a system and a terminal and also to reduce theamount of work for testing the system and the terminal.

Table format 5 as illustrated in FIG. 10 may be defined in advance inmemory 102. That is, the combination of CFI values differs every subsetin this type of table format. This type of table format is useful as thetable format capable of allocating four CCs or five CCs.

Here, table format 1 is described as a format for three CCs and tableformats 2 to 4 are each described as a format for four CCs or five CCsin FIG. 9. It is, however, possible to separately define, as a formatfor four CCs, the table format in which subset 1 includes CIFs=2, 3, and4, subset 2 includes CIFs=5 and 6, and subset 3 includes CIFs=7 and 8.By this means, it is possible to maximize the number of CFIs that can benotified every CC.

Other Embodiments

(1) The above embodiments have explained that a PDCCH of each CC is usedto report a CFI of the CC, while a PDCCH of a certain CC is used toreport a CFI of another CC. However, the present invention is notlimited to this, and the PDCCH of each CC may not need to report the CFIof the CC. That is, the configuration in which only the PDCCH of acertain CC reports the CFI of another CC is also possible. In this case,when a CC used to transmit a PDCCH including information of a CC to beadded at the moment of CC addition is the same as the CC to be added,terminal 200 considers that the PDCCH does not include any CIF and thusdetermines that no CIF code point is notified or that the CIF code pointis notified, but the allocation is invalid. Meanwhile, when the CC usedto transmit the PDCCH including the information of the CC at the momentof CC addition is different from the CC to be added, terminal 200considers that the PDCCH includes a CIF and thus determines that the CIFcode point is notified. In this case, there is no need to separatelyreport the information indicating whether or not the CIF is included,every PDCCH. Also, even in the system performing operations with a CIFand without the CIF every CC, when adding a CC to a UE CC set, terminal200 only needs to determine whether the CC to be added performs CIFnotification or the CC different from the CC to be added performs theCIF notification. Here, terminal 200 only has to operate commonly inboth cases. Thus, it is possible to simplify the system and theterminal.

(2) The above embodiments have explained that RRC signaling is performedat addition or deletion of the UE CC set. However, the present inventionis not limited to this and is applicable even when more dynamic controlthan RRC signaling is performed. For example, it is also possible todesignate the CIF code point even when a MAC header or a PDCCH reportsthe addition or deletion of the CC (that is, CCactivation/deactivation).

(3) The above embodiments have explained that one PDCCH is transmittedper CC. However, the present invention is not limited to this, and twoor more PDCCHs may be transmitted per CC. In case of this configuration,at the addition of a CC, CIF code points are allocated to two ore morePDCCH CCs included in one CC.

(4) The above embodiments have explained that CFI indicates a controlchannel region. However, the present invention is not limited to this,and the CFI may be the information indicating the first OFDM symbol towhich data is mapped. For example, while CFI=2 holds true in a certainCC (that is, up to two OFDM symbols are used for control channel), thefirst OFDM symbol number to which data for a certain terminal 200 ismapped may be 4. For example, even in a case where only CFI=3 can benotified to a certain terminal 200 in a certain CC, it is possible toconfigure a small control channel region (for example, two OFDM symbols)when the amount of control channel of the CC is small.

(5) Although a case where the number of bits in the CIF is 2 bits and 3bits has been described in the above, another number of bits is alsopossible. Also, a case where a cell or a terminal uses a differentnumber of bits may be possible.

(6) Although an example to report the CI and CFI in the CIF has beendescribed in the above, the present invention is applicable forreporting information other than the CFI.

(7) Although the above embodiments have described allocation of downlinkCC, the techniques described in embodiments are also applicable forallocation of uplink CC. Also, a CC may be added or deleted in a pair ofuplink and downlink, or may be added or deleted in uplink and downlinkseparately.

(8) The above described UE CC set may be referred to as “UE DL CC set”for a downlink CC and “UE UL CC set” for an uplink CC.

(9) The above mentioned PDCCH format may be referred to as “DCI(Downlink Control Information) format.”

(10) The above mentioned “carrier aggregation” may also be referred toas “band aggregation.” Furthermore, discontinuous frequency bands may beaggregated in the carrier aggregation.

(11) Although the above mentioned “component carrier” has been definedas the band having a width of maximum 20 MHz and the basic unit ofcommunication bands, the component carrier may be defined as follows. A“component carrier” in downlink (hereinafter referred to as “downlinkcomponent carrier”) may be defined as the band divided by downlinkfrequency band information in the BCH broadcasted from a base station,or the band defined by a bandwidth where a physical downlink controlchannel (PDCCH) is placed in the frequency domain in a distributedmanner. Also, a “component carrier” in uplink (hereinafter referred toas “uplink component carrier”) may be defined as the band divided byuplink frequency band information in the BCH broadcasted from a basestation, or the reference unit in the communication band which is equalto or below 20 MHz and includes a PUCCH near the center and PUCCHs atboth end parts. Also, in 3GPP LTE, “component carrier(s) (CC)” may beexpressed as “Component Carrier(s)” in English. Also, “componentcarrier(s)” may be referred to as “component band(s).”Furthermore,“Component Carrier” may be defined by a physical cell number and acarrier frequency number, and may be referred to as “cell.”

(12) The PDCCH may be set to be always transmitted by the primarycomponent carrier. Here, the primary component carrier may be thecomponent carrier determined by a system (for example, the componentcarrier used for transmitting an SCH or PBCH), a common componentcarrier among terminals 200 may be set for each cell, or a differentcomponent carrier may be set for each terminal 200.

(13) Although the above embodiments have described an example where thepresent invention is implemented with hardware, the present inventioncan be implemented with software.

Furthermore, each function block employed in the explanation of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Furthermore, the method of circuit integration is not limited to LSI' s,and implementation using dedicated circuitry or general purposeprocessors is also possible. After LSI manufacture, utilization of aprogrammable FPGA (Field Programmable Gate Array) or a reconfigurableprocessor where connections and settings of circuit cells within an LSIcan be reconfigured is also possible.

Furthermore, if integrated circuit technology comes out to replace LSI'sas a result of the advancement of semiconductor technology or aderivative other technology, it is naturally also possible to carry outfunction block integration using this technology. Application ofbiotechnology is also possible.

The disclosure of Japanese Patent Application No. 2010-030267, filed onFeb. 15, 2010, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The transmission apparatus and the transmission method of the presentinvention are useful as an apparatus and a method capable of preventing,when adding a CC to be used in carrier aggregation communication, adelay in data transmission while suppressing an increase in the numberof bits required for notification of the CCs in use.

REFERENCE SIGNS LIST

100 Base station

101 Configuration section

102 Memory

103 Control section

104 PDCCH generating section

105, 106, 107 Coding section

108, 109, 110, 210, 211 Modulating section

111 Allocation section

112 PCFICH generating section

113 Multiplexing section

114, 214 IFFT section

115, 215 CP adding section

116, 216 RF transmitting section

117, 201 RF receiving section

118, 202 CP removing section

119, 203 FFT section

120 Extraction section

121 IDFT section

122 Data receiving section

200 Terminal

204 Demultiplexing section

205 Configuration information receiving section

206 PCFICH receiving section

207 CIF table configuring section

208 PDCCH receiving section

209 PDSCH receiving section

212 DFT section

213 Mapping section

1. A communication apparatus comprising: control circuitry which, inoperation, generates configuration information, wherein, when acomponent carrier is added, the configuration information indicates acarrier indicator field value (CIF value) assigned to the addedcomponent carrier and a component carrier identification index (CC IDindex) of the added component carrier, wherein the CIF value and the CCID index of the added component carrier are added to a one-to-onecorrespondence relationship between one or more CIF values and one ormore CC ID indexes, wherein the CIF value assigned to the addedcomponent carrier is a previously unconfigured CIF and the one-to-onecorrespondence relationship prior to the addition is maintained, andwhen a component carrier is deleted, the configuration informationindicates the CC ID index of the deleted component carrier, wherein theCIF value of the deleted component carrier is deleted from theone-to-one correspondence relationship; and a transmitter, which iscoupled to the control circuitry and which, in operation, transmits theconfiguration information to a terminal apparatus.
 2. The communicationapparatus according to claim 1, wherein the control circuitry, inoperation, generates resource allocation information, which indicatesthe CIF value of the component carrier allocated to the terminalapparatus.
 3. The communication apparatus according to claim 1, whereinthe CIF values are assigned to component carriers that are used totransmit data.
 4. The communication apparatus according to claim 1,wherein the one-to-one correspondence relationship is configured foreach terminal apparatus.
 5. A communication method comprising:generating configuration information, wherein, when a component carrieris added, the configuration information indicates a carrier indicatorfield value (CIF value) assigned to the added component carrier and acomponent carrier identification index (CC ID index) of the addedcomponent carrier, wherein the CIF value and the CC ID index of theadded component carrier are added to a one-to-one correspondencerelationship between one or more CIF values and one or more CC IDindexes, wherein the CIF value assigned to the added component carrieris a previously unconfigured CIF and the one-to-one correspondencerelationship prior to the addition is maintained, and when a componentcarrier is deleted, the configuration information indicates the CC IDindex of the deleted component carrier, wherein the CIF value of thedeleted component carrier is deleted from the one-to-one correspondencerelationship; and transmitting the configuration information to aterminal apparatus.
 6. The communication method according to claim 5,comprising: generating resource allocation information, which indicatesthe CIF value of the component carrier allocated to the terminalapparatus.
 7. The communication method according to claim 5, wherein theCIF values are assigned to component carriers that are used to transmitdata.
 8. The communication method according to claim 5, wherein theone-to-one correspondence relationship is configured for each terminalapparatus.